Process for preparing a graft polyolefin

Abstract

A process for making a grafted polyolefin having improved yellowness properties, the process comprising reacting a blend of: (i) at least one polyolefin; (ii) at least one monomer; wherein the at least one monomer is selected from one or more acid compounds having the following general chemical formula (I) or formula (II): wherein in formula (I) and formula (II), R1 or R2 is H, with the proviso that neither R1 nor R2 is H; wherein at least one of R1 and R2 is an alkyl or alkenyl group having 1 to 20 carbon atoms; and wherein R1, R2, or both R1 and R2 can further comprise an ester, a heteroatom, an aryl group, or a halogen; and (iii) at least one radical initiator to form a grafted polyolefin; wherein the grafted polyolefin has lt; and the yellowness index YIE313 of the product is 30. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a method for manufacturing grafted polyolefin; and more particularly, the present invention relates to a grafting method for manufacturing grafted polyolefin by grafting polyolefin with methyl / dimethyl maleic anhydride so as to reduce yellowing of the grafted polyolefin after grafting the polyolefin with methyl / dimethyl maleic anhydride. Background Art

[0002] In many packaging applications (such as food, pharmaceuticals, cosmetics, transportation, electronic components, metal laminates, etc.), polyolefins are required to bond to different substrates, thus requiring a tie layer adhesive. To date, maleic anhydride grafted polyolefins (MAH-g-polyolefins) have been widely used in tie layer adhesives.

[0003] Typically, MAH-g-polyolefins are produced by grafting maleic anhydride (MAH) onto the polyolefin backbone with the aid of an organic peroxide via high temperature twin screw extrusion. For unknown reasons, the addition of peroxides often results in an undesirable yellowness.

[0004] In some color-sensitive applications, light-colored or colorless materials are desired; however, undesirable yellowing or even dark yellowing often occurs in MAH-g-polyolefins and their related diluted products. Such materials with undesirable yellowing are not desirable for use in color-sensitive applications.

[0005] In some cases, attempts have been made to address the color problem by adding certain additives to MAH-g-polyolefins. For example, U.S. Pat. No. 6,380,320 B1 discloses the preparation of anhydride grafted polymers with improved color properties by mixing a polyolefin, an anhydride-providing monomer, and an oxoboron compound additive in an extruder; and subsequently extruding the resulting anhydride grafted polymer into a shaped article. Although some success has been achieved in reducing the yellowness of anhydride grafted polymers, there is still a need for lighter colored or colorless materials for use in color-sensitive applications. Therefore, in addition to using MAH-g-polyolefins alone or in combination with other additives, it is desirable to provide an anhydride grafted polyolefin with reduced yellowness for use in color-sensitive applications.

[0006] U.S. Pat. No. 5,728,776A discloses a method for preparing a grafted polyolefin by melt-kneading (a) a polyolefin (A), (b) a radically polymerizable monomer (B) and (c) a radical polymerization initiator (C), the radically polymerizable monomer being an unsaturated carboxylic anhydride and heat-treated at 50° C. to 250° C. before the grafting reaction. Component (A) is polypropylene. The unsaturated carboxylic anhydride has a cyclic anhydride structure and is at least one selected from maleic acid, fumaric acid, itaconic acid, and citraconic acid. The unsaturated carboxylic acid is at least one selected from MAH, itaconic anhydride, citraconic anhydride and cyclopentanedicarboxylic anhydride. Component (C) is an organic peroxide.

[0007] CN5859970A discloses a method for improving the grafting efficiency of polyolefins. The method comprises: weighing polyolefins, polar monomers (part of the polar monomers are in a solvent), initiators and antioxidants according to weight parts. The method comprises: adding the initiator to anhydrous ethanol, polyolefins, antioxidants and polar monomer solutions in a high-speed mixer to mix uniformly. After adding a volatile solvent for the polar monomer, the resulting mixture is added to an extruder hopper. The temperature of each section of the extruder is between 220°C and 140°C; the extruder maintains a main screw speed of 60rpm to 400rpm and a screw feed speed of 10rpm to 80rpm, while at the same time pumping an anhydrous ethanol solution of the initiator into an extruder with different heating sections according to different speeds. Subsequently, the resulting extrudate is cooled, dried and cut to obtain polyolefin particles grafted and modified with polar monomers.

[0008] The above two references disclose grafting methods for improving polyolefins. In the methods disclosed in the above references, one of the selected grafting components can be MAH. However, there is no disclosure of obtaining a light-colored or colorless grafted polyolefin product; and there is no mention in the above references that methyl / dimethyl maleic anhydride can be used to produce products with improved color. The above references do not disclose the use of methyl / dimethyl maleic anhydride instead of MAH to reduce and / or solve color problems. Summary of the invention

[0009] One embodiment of the present invention relates to a method for making a grafted polyolefin, the method comprising: grafting a polyolefin with methyl / dimethyl maleic anhydride so that the grafted polyolefin has improved yellowness characteristics. The method for making a grafted polyolefin with improved yellowness characteristics comprises reacting a blend of: (i) at least one polyolefin; (ii) at least one monomer; wherein the at least one monomer is selected from one or more acid compounds having the following general chemical formula (I) or general chemical formula (II):

[0010] or

[0011]

[0012] wherein in formula (I) and formula (II), R1 or R2 is H, provided that both R1 and R2 are not H; wherein at least one of R1 and R2 is an alkyl or alkenyl group having 1 to 20 carbon atoms; and wherein R1, R2 or both R1 and R2 may also include esters, heteroatoms, aromatic groups or halogens; and (iii) at least one free radical initiator to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of <30.

[0013] In some embodiments, the method of the present invention comprises the following steps: first, providing the following components: (i) at least one polyolefin; (ii) at least one monomer; for example, wherein the at least one monomer has formula (I) or formula (II); and (iii) at least one free radical initiator; second, mixing the at least one polyolefin, the at least one monomer (such as a monomer selected from 3-methylfuran-2,5-dione, 3,4-dimethylfuran-2,5-dione or a combination thereof) and the at least one free radical initiator to form a reactive blend; and then, reacting the blend or allowing the reactive blend to react to form a grafted polyolefin. The resulting grafted polyolefin advantageously exhibits a yellowness index YIE313 of <30. Therefore, the resulting grafted polyolefin can be used to produce films or other articles with low yellowness, which in turn can be used in color-sensitive applications requiring light-colored or colorless materials.

[0014] One object of the present invention is to reduce color formation during grafting of anhydrides onto polyolefins. It has been found that methyl / dimethyl maleic anhydride reduces yellowing of the grafted polyolefin compared to polyolefins grafted with MAH. Without being limited to any particular theory, it is theorized that based on 1 Based on H NMR (proton nuclear magnetic resonance) analysis and pyrolysis results, the mechanism of color generation in MAH grafting may be the result of phenol products and quinone products present in the final grafted polyolefin prepared by MAH grafting. On the other hand, it is believed that methyl / dimethyl maleic anhydride grafting suppresses the generation of phenol products and quinone products; and therefore, provides an anhydride grafted polyolefin product with better color properties. DETAILED DESCRIPTION

[0015] Temperatures used herein are in degrees Celsius (°C).

[0016] Unless otherwise stated, "room temperature (RT)" and / or "ambient temperature" herein means a temperature between 20°C and 26°C.

[0017] The term "composition" as used herein refers to a mixture of materials comprising the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0018] The terms "comprising", "including", "having" and their derivatives are not intended to exclude the presence of any additional components, steps or procedures, whether or not they are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all compositions claimed by using the term "comprising" may include any additional additives, adjuvants or compounds, whether in polymeric form or otherwise. In contrast, the term "consisting essentially of excludes any other components, steps or procedures (except those that are not essential to operability) from the scope of any subsequent statements. The term "consisting of" excludes any components, steps or procedures that are not specifically described or listed. Unless otherwise stated, the term "or" refers to the listed members individually and in any combination. The use of the singular includes the use of the plural, and vice versa.

[0019] The numerical range disclosed herein includes all values ​​from the lower limit to the upper limit, and includes the lower limit and the upper limit. For a range containing explicit values ​​(e.g., a range of 1 or 2 or 3 to 5 or 6 or 7), any sub-range between any two explicit values ​​is included (e.g., the above range 1 to 7 includes sub-ranges of 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc.).

[0020] As used throughout this specification, the abbreviations given below have the following meanings, unless the context clearly indicates otherwise: "=" means "equal to" or "equal to"; "<" means "less than"; ">" means "greater than"; "≤" means "less than or equal to"; "≥" means "greater than or equal to"; "@" means "at"; ppm = parts per million; ppb = parts per billion; ppt = parts per trillion; BV / hr = bed volume / hour; "MT" = metric ton; g = gram; mg = milligram; Kg = kilogram; L = liter; g / L = gram per liter; μL = microliter; "g / cm 3 " or "g / cc" = grams per cubic centimeter; g / 10min = grams per 10 minutes; mg / mL = milligrams per milliliter; "kg / m 3 = kilogram per cubic meter; ppm = parts per million by weight; pbw = parts by weight; rpm = revolutions per minute; m = meter; mm = millimeter; cm = centimeter; μm = micrometer; nm = nanometer; min = minute; s = second; ms = millisecond; hr = hour; Pa = Pascal; MPa = megapascal; Pa-s = Pascal second; mPa-s = millipascal second; g / mol = gram per mole; g / eq = gram per equivalent; M n = number average molecular weight; M w = weight average molecular weight; pts = parts by weight; 1 / s or sec -1 = countdown seconds [s -1]; °C = degrees Celsius; °C / min = degrees Celsius per minute; psi = pounds per square inch; kPa = kilopascals; % = percent; vol% = volume percent; mol% = mole percent; and wt% = weight percent.

[0021] Specific embodiments of the present invention are described herein below. These embodiments are provided so that this disclosure will be thorough and complete; and will fully convey the scope of the subject matter of the present invention to those skilled in the art.

[0022] Unless stated to the contrary, implicit from the context, or customary in the art, all percentages, parts, ratios, etc. are by weight, all temperatures are in ° C., and all test methods are current as of the filing date of this disclosure.

[0023] Generally, the method of the present invention for making a grafted polyolefin having improved yellowness characteristics comprises: reacting a reactive blend, or allowing a reactive blend to react, wherein the reactive blend comprises the following components: (i) at least one polyolefin; (ii) at least one monomer; wherein at least one monomer is selected from the group consisting of 3-methylfuran-2,5-dione, 3,4-dimethylfuran-2,5-dione, or a combination thereof; and (iii) at least one free radical initiator. By blending at least one polyolefin, at least one monomer, and at least one free radical initiator under process conditions (such as elevated temperature), a grafted polyolefin is formed; wherein the grafted polyolefin has a yellowness index YIE313 of <30. If desired, other optional additives or agents or compounds (optional component (iv)) may be added to the above polyolefin composition.

[0024] Component (i) of the formulation or composition for producing the grafted polyolefin of the present invention having improved yellowness characteristics is at least one polyolefin. Examples of polyolefins (component (i)) useful in the present invention include: polyethylene; polypropylene; styrene-ethylene-butylene-styrene; -olefin homopolymers or copolymers; ethylene-octene copolymers; ethylene-hexene copolymers; ethylene-propylene copolymers; ethylene; propylene; norbornene-diene copolymers; copolymers of ethylene with unsaturated esters (such as vinyl acetate and alkyl acrylates) (such as ethylene-vinyl acetate, ethylene-ethyl acrylate, etc.); and mixtures thereof.

[0025] Examples of some commercially available polyolefins that can be used to prepare the grafted polyolefins of the present invention include, for example, NORDEL TM 4725、DOW TM LDPE 310E, VERSIFY TM 2300 (both available from The Dow Chemical Company); and mixtures thereof.

[0026] In one general embodiment, the concentration of the polyolefin (component (i)) that can be used to prepare the grafted polyolefin composition can range from 90.0 wt % to 99.9 wt %; in another embodiment, 95.0 wt % to 99.0 wt %, and in yet another embodiment, 97.0 wt % to 99.0 wt %, based on the total weight of all components in the composition.

[0027] Component (ii) of the formulation or composition for producing the grafted polyolefin of the present invention having improved yellowness characteristics is at least one monomer. For example, the monomer (component (ii)) may include 3-methylfuran-2,5-dione; 3,4-dimethylfuran-2,5-dione; 3-ethylfuran-2,5-dione; 3,4-diethylfuran-2,5-dione; and combinations thereof.

[0028] The concentration range of the monomer (component (ii)) that can be used to prepare the grafted polyolefin with improved yellowness characteristics of the present invention can be 0.05 wt % to 5.0 wt % in one general embodiment, 0.5 wt % to 3.0 wt % in another embodiment, and 1.0 wt % to 2.5 wt % in yet another embodiment, based on the total weight of all components in the composition. Using a concentration above 5.0 wt % may make it difficult to graft the polymer; and a content below 0.05 wt % may not provide sufficient grafting on the polymer.

[0029] Component (iii) of the formulation or composition for producing the grafted polyolefin of the present invention having improved yellowness characteristics is at least one free radical initiator. Any free radical initiator known to those skilled in the art of grafting can be used in the present invention. For example, the free radical initiator (component (iii)) may include: dialkyl peroxides and hydroperoxides; diacyl peroxides; peresters; organic polyoxides; azo compounds; and combinations thereof.

[0030] Examples of some commercially available free radical initiators that can be used to prepare the grafted polyolefins of the present invention include dicumyl peroxide ("DCP"); benzoyl peroxide ("BPO"); azobisisobutyronitrile ("AIBN"); t-butyl peroxybenzoate; di-t-amyl peroxide ("DTAP"); bis(t-butylperoxyisopropyl)benzene ("BIPB"); isopropylcumyl t-butyl peroxide; t-butylcumyl peroxide; Di-tert-butyl oxide; 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane; 2,5-bis(tert-butylperoxy)-2,5-dimethylhexyne-3; 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane; isopropylcumylcumyl peroxide; butyl 4,4-di(tert-butylperoxy)valerate; di(isopropylcumyl) peroxide; 1,1-di-(tert-butylperoxy)cyclohexane (e.g. 331"); 1,1-di-(tert-amylperoxy)cyclohexane (e.g., Luperox ); tert-butyl peroxyacetate ("TBPA"); tert-amyl peroxyacetate ("TAPA"); 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (e.g., 101); tert-butylperoxy-2-ethylhexyl carbonate ("TBEC"); 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (e.g., 301); and mixtures thereof.

[0031] In a preferred embodiment, the free radical initiator (component (iii)) of the composition of the present invention comprises, consists essentially of, or consists of: DCP; BPO; and mixtures thereof.

[0032] The concentration of the free radical initiator (component (iii)) that can be used to prepare the grafted polyolefin with improved yellowness characteristics of the present invention can be 0.01 wt % to 3.00 wt % in one general embodiment, 0.05 wt % to 2.00 wt % in another embodiment, and 0.1 wt % to 1.00 wt % in yet another embodiment, based on the total weight of all components in the composition. Using a concentration above 3.00 wt % may result in gelation; and a content below 0.1 wt % may not provide sufficient grafting on the polymer.

[0033] Optionally, the composition of the present invention can be formulated with a variety of additives to achieve the performance of specific functions while maintaining the excellent benefits / properties of the composition of the present invention. For example, the optional additives (component (iv)) that can be used in the composition of the present invention can be selected from the group consisting of: colorants; mineral fillers, processing oils; flame retardants, foaming agents; processing aids, antioxidants; and mixtures thereof.

[0034] The optional compounds used to prepare the grafted polyolefins having improved yellowness characteristics of the present invention may be present in amounts generally ranging from 0 wt % to 10 wt % in one embodiment; from 0.01 wt % to 5 wt % in another embodiment; and from 0.1 wt % to 1 wt % in yet another embodiment.

[0035] In a broad embodiment, the method of the present invention for preparing a grafted polyolefin having improved yellowness characteristics comprises reacting a blend of: (i) at least one polyolefin; (ii) at least one monomer; wherein at least one monomer is selected from the group consisting of: 3-methylfuran-2,5-dione; 3,4-dimethylfuran-2,5-dione; or a combination thereof; and (iii) at least one free radical initiator to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of <30. One or more additional optional components, additives, agents or compounds (component (iv)) may be added to the composition if desired.

[0036] The above-mentioned composition, formulation or blend is formed by mixing, blending or mixing the following materials under process conditions: (i) at least one polyolefin; (ii) at least one monomer; wherein the at least one monomer is selected from the group consisting of: 3-methylfuran-2,5-dione; 3,4-dimethylfuran-2,5-dione; or a combination thereof; and (iii) at least one free radical initiator; to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of <30. For example, components (i), (ii), (iii) and optionally (iv) can be mixed together in the desired concentrations discussed above to form a reactive blend; and then, the reactive blend can be heated at a temperature of 140°C to 220°C in one embodiment; at a temperature of 160°C to 220°C in another embodiment; and at a temperature of 180°C to 220°C in yet another embodiment to provide a reaction for forming the grafted polyolefin. If desired, optional additives (component (iv)) may be mixed with any one or more of components (i), (ii) and (iii). The order in which the components are mixed is not critical; and two or more components may be mixed together followed by the addition of the remaining components. The formulation components may be mixed together by any conventional mixing method and equipment known to those skilled in the art of mixing.

[0037] In other embodiments, the method for preparing the composition of the present invention and forming a grafted polyolefin with improved yellowness characteristics comprises the following steps: (a) providing the following components: (i) at least one polyolefin; (ii) at least one monomer; wherein at least one monomer is selected from the group consisting of: 3-methylfuran-2,5-dione; 3,4-dimethylfuran-2,5-dione; or a combination thereof; (iii) at least one free radical initiator; and (iv) optionally an additive; and (b) mixing at least one polyolefin, at least one monomer, at least one free radical initiator, and any optional additives (if desired) to form a reactive blend. Mixing can be performed using methods and equipment known to those skilled in the art (such as an extruder) to form a reactive blend; and (c) reacting the reactive blend or allowing the reactive blend to react (e.g., by heating the blend at an elevated temperature (e.g., a temperature above the melting temperature of the polyolefin)) to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of <30.

[0038] For example, in step (c) above, the reactive blend of components (i), (ii), (iii), and optionally (iv) above may be heated at a temperature of 140°C to 240°C in one embodiment; 160°C to 240°C in another embodiment; and 180°C to 240°C in yet another embodiment, sufficient to form the grafted polyolefin of the present invention.

[0039] The resulting grafted polyolefin formed as described above may be further processed by methods well known to those skilled in the art to form shaped or finished parts or articles.

[0040] The grafted polyolefin of the present invention prepared according to the above method has several advantageous properties and / or benefits. For example, some of the properties / benefits exhibited by the grafted polyolefin of the present invention include: For example, in a general embodiment, the grafted polyolefin has a yellowness index YIE313 of <30.

[0041] In some embodiments, the grafted polyolefin has a yellowness index YIE313 of <30 in one general embodiment, <15 in another embodiment, and <5 in yet another embodiment. In other embodiments, the grafted polyolefin has a yellowness index YIE313 of 0 to <30 in one embodiment; 10 to <30 in another embodiment; and 20 to <30 in still another embodiment. The yellowness index is measured by the following procedure described in the Yellowness Index Test in the Examples, including testing on a Hunterlab ColorQuest XE (available from Hunterlab) with a D65 illuminant with a 10° observer and a reflectance model using an approximately 2 mm single-layer film prepared by the method described in the Examples.

[0042] The grafted polyolefins of the present invention can be used, for example, as adhesive layers, compatibilizers, impact modifiers, crosslinkable polyolefins, and the like in applications where such materials are useful.

[0043] Example

[0044] The following Inv.Ex. and Comp.Ex. (collectively referred to as "Examples") are given herein to further illustrate the features of the present invention, but are not intended to be construed as limiting the scope of the claims, either explicitly or by implication. The Inv.Ex. of the present invention are represented by Arabic numerals, and the Comp.Ex. are represented by letters of the alphabet. The following experiments analyze the performance of embodiments of the compositions described herein. Unless otherwise indicated, all parts and percentages are by weight based on total weight.

[0045] name

[0046] Some of the names and abbreviations of the materials and items used in the examples are as follows:

[0047] "MAH" means maleic anhydride.

[0048] "MFD" means 3-methylfuran-2,5-dione.

[0049] "DMFD" means 3,4-dimethylfuran-2,5-dione.

[0050] "DCP" stands for dicumyl peroxide.

[0051] "MI" stands for melt index.

[0052] "ENB" means ethylidene norbornene.

[0053] "FTIR" stands for Fourier Transform Infrared.

[0054] "ATR" stands for attenuated total reflectance.

[0055] "TD" stands for thermal desorption.

[0056] "Py" means pyrolysis.

[0057] "EGA" stands for evolved gas analysis.

[0058] "GC" stands for gas chromatography.

[0059] "MS" means mass spectrometry.

[0060] "EI" stands for electron impact, which is a form of ionization.

[0061] "PFTBA" stands for perfluorotributylamine, a chemical used to tune mass spectrometers.

[0062] The "CIELAB color space" or "L*a*b*" is a well-known color space defined by the International Commission on Illumination (abbreviated to CIE). The name "L*a*b*" expresses color as three values: "L*" represents perceived brightness, and "a*" and "b*" represent the four unique colors of human vision: red, green, blue and yellow. It is used in industry to detect small differences in color.

[0063] raw materials

[0064] The relevant raw materials (ingredients) used in the examples are described in Table I.

[0065] Table I - Raw Materials / Ingredients

[0066]

[0067]

[0068] Preparation

[0069] General process for preparing grafted polyolefins

[0070] The ingredients / formulations used to produce the grafted polyolefins in the examples are described in Table II. Components (i) to (iii) and optionally (iv) were blended using a Brabender mixer and using the following general process steps: (1) a polymer (e.g., Polymer 1, Polymer 2, or Polymer 3) was fed into a Brabender mixer set at 120°C and a rotor speed of 10 rpm; (2) a peroxide (e.g., Peroxide 1) and an anhydride (e.g., Anydride 1, Anydride 2, or Anydride 3) were fed into the polymer melt in the mixer at the set temperature to form a reactive blend; (3) the resulting blend of ingredients was subjected to final mixing at a temperature of 180°C and a rotor speed of 45 rpm for 10 min; and (4) the resulting compound from the mixer was collected for analysis.

[0071] Table II - Formulations

[0072]

[0073] Analysis and testing methods

[0074] FTIR testing

[0075] The sample of grafted polyolefin polymer was examined by Fourier transform infrared (FTIR) spectroscopy using a single reflection attenuated total reflection (ATR) accessory equipped with a diamond crystal. The penetration depth was estimated to be 2 μm during ATR analysis. Thermo Electron Nicolet 5700 optical bench (available from Thermo Electron) was used to collect spectra by 32 scans at a resolution of 4 cm-1. The successful grafting of the sample was confirmed using FTIR analysis.

[0076] Yellowing index test

[0077] The method for measuring the yellowing index of a film sample (referred to herein as the "yellowing index test" or "YI test") is performed as follows: A single-layer film sample is prepared by heat-pressing about 20 g of a grafted polyolefin polymer using a heat press to obtain a single-layer film of about 2 mm as follows:

[0078] 1. Use a mold with the following dimensions: 100 mm x 100 mm x 2 mm.

[0079] 2. Weigh approximately 20 g of pellets / pieces and place in a mold.

[0080] 3. The mold was clamped between the upper and lower plates of a hot press at 0 MPa; and the mold was preheated at 120° C. for 10 min.

[0081] 4. Maintain the mold at 120°C and 5 MPa for 0.5 min.

[0082] 5. Maintain the mold at 120°C and 10 MPa for 0.5 min.

[0083] 6. After venting (to degas any potential air present in the resin) 8 times, the mold was kept at 180°C and 10 MPa for about 13 min.

[0084] 7. Cool the mold from 180°C to 60°C within 10 min at 10 MPa.

[0085] 8. The monolayer film formed in the mold was removed from the mold for testing.

[0086] The resulting monolayer film was subjected to a YI test. The yellowing index test using the YI test of the monolayer film prepared as described above was carried out on a Hunterlab ColorQuest XE (available from Hunterlab) with a D65 light source with a 10° observer and a reflection model. The measurement results of the yellowing index (YIE313) obtained using the YI test are described in Table III. It should be noted that the YIE313 number depends on sample preparation. The ASTM D1925 procedure is a standard for how to test the index YIE313 number, but the ASTM D1925 procedure does not cover the preparation of the specimen to be tested for yellowness. The YIE313 number is only comparable between samples prepared using the same sample preparation procedure.

[0087] Table III - Characteristics / Performance of Grafted Polyolefin Products

[0088]

[0089] Results and Discussion

[0090] The results described in the above table show that the grafted polyolefins of the inventive examples have much better color properties than the grafted polyolefins of the comparative examples. For example, the polyolefins used in inventive examples 1 and 4 are the same as the polyolefins used in comparative example A; and when the grafted polyolefins of inventive examples 1 and 4 are compared with the grafted polyolefin of comparative example A, the grafted polyolefins of inventive examples 1 and 4 show much better color (less yellowing) than the grafted polyolefin of comparative example A, wherein the grafted polyolefin in comparative example A is grafted with MAH.

[0091] In another example, the polyolefin used in Inventive Examples 2 and 5 is the same as the polyolefin used in Comparative Example B. And when the grafted polyolefins of Inventive Examples 2 and 5 are compared with the grafted polyolefin of Comparative Example B, the grafted polyolefins of Inventive Examples 2 and 5 show much better color (less yellowing) than the grafted polyolefin of Comparative Example B, where the grafted polyolefin is grafted with MAH.

[0092] In yet another example, the polyolefin used in Inventive Examples 3 and 6 is the same as the polyolefin used in Comparative Example C; and when the grafted polyolefins of Inventive Examples 3 and 6 are compared with the grafted polyolefin of Comparative Example C, the grafted polyolefins of Inventive Examples 3 and 6 show much better color (less yellowing) than the grafted polyolefin of Comparative Example C, wherein the grafted polyolefin in Comparative Example C is grafted with MAH.

Claims

1. A process for producing a grafted polyolefin having improved yellowness characteristics, the process comprising reacting a blend of: (i) at least one polyolefin; (ii) at least one monomer; wherein the at least one monomer is selected from one or more acid compounds having the following general chemical formula (I): or Wherein the at least one monomer is selected from one or more hydrolyzed acid compounds having the following general chemical formula (II): wherein in formula (I) and formula (II), R1 or R2 is H, provided that both R1 and R2 are not H; wherein at least one of R1 and R2 is an alkyl or alkenyl group having 1 to 20 carbon atoms; and wherein R1, R2, or both R1 and R2 can also include an ester, a heteroatom, an aryl group, or a halogen; and (iii) at least one free radical initiator to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of less than 30 as determined according to the YI Test.

2. The method of claim 1, wherein the grafted polyolefin has a yellowness index YIE313 of 0 to less than 30 as determined according to the YI Test.

3. The method according to claim 1, wherein the grafted polyolefin grafted with the monomer of component (ii) has an improved yellowness index YIE313 as determined according to the YI test of 30% to 70% compared to the grafted polyolefin grafted with maleic anhydride. 4 . The method of claim 1 , wherein the at least one monomer is selected from the group consisting of 3-methylfuran-2,5-dione, 3,4-dimethylfuran-2,5-dione, or a combination thereof.

5. The method of claim 1, wherein the at least one polyolefin is polyethylene; ethylene-α-olefin copolymers; ethylene-α-olefin diene terpolymers; and mixtures thereof.

6. The method of claim 1, wherein the at least one free radical initiator is a peroxide selected from the group consisting of: dicumyl peroxide; bis(tert-butylperoxyisopropyl)benzene; tert-butylcumyl peroxide; di-tert-butyl peroxide; 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane; 2,5-bis(tert-butylperoxy)-2,5-dimethylhexyne-3; and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

7. The method of claim 1, wherein the concentration of the at least one polyolefin is from 95.0 wt% to 99.9 wt%; wherein the concentration of the at least one monomer is from 0.1 wt% to 5.0 wt%; and wherein the concentration of the at least one free radical initiator is from 0.01 wt% to 3.0 wt%.

8. The process of claim 1, wherein the process is conducted at a temperature above the melting point of the polyolefin.

9. The method of claim 1, wherein the method is performed at a temperature of 50°C to 350°C.

10. The process according to claim 1, wherein the process is carried out in a continuous process using an extruder; or wherein the process according to claim 1 is carried out in a batch process using a mixing vessel.

11. A method according to any one of the preceding claims, further comprising the step of forming the grafted polyolefin into a shaped product or article.

12. A product or article formed by the method according to any one of the preceding claims.

13. The product or article of claim 12, wherein the product or article is a film, pellets or granules.

14. A composition for making a grafted polyolefin having improved yellowness characteristics, the composition comprising a reaction mixture of: (i) at least one polyolefin; (ii) at least one monomer; wherein the at least one monomer is selected from one or more acid compounds having the following general chemical formula (I): or Wherein the at least one monomer is selected from one or more hydrolyzed acid compounds having the following general chemical formula (II): wherein in formula (I) and formula (II), R1 or R2 is H, provided that both R1 and R2 are not H; wherein at least one of R1 and R2 is an alkyl or alkenyl group having 1 to 20 carbon atoms; and wherein R1, R2, or both R1 and R2 can also include an ester, a heteroatom, an aryl group, or a halogen; and (iii) at least one free radical initiator to form a grafted polyolefin; wherein the grafted polyolefin has a yellowness index YIE313 of less than 30.

15. The composition of claim 14, wherein the grafted polyolefin grafted with the monomer of component (ii) has an improved yellowness index YIE313 as determined according to the YI test of at least 30% to 70% compared to a grafted polyolefin grafted with maleic anhydride.

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